1. Field of the Invention
The invention relates generally to pixel sensor cells, design structures for fabrication thereof and methods for operation thereof. More particularly, the invention relates to pixel sensor cells with enhanced dynamic range capabilities.
2. Description of the Related Art
Solid state sensors are popular optoelectronic components that find use in various technology applications, including in particular imaging technology applications. Particularly common are solid state sensors that are used as active light capture and imaging elements within digital cameras.
Solid state image sensors may be fabricated using any of several semiconductor technologies for the active light capture and imaging elements. Charge coupled devices (CCDs) are known as more traditional solid state image sensor light capture and imaging elements. Complementary metal oxide semiconductor (CMOS) devices provide yet another semiconductor based active light capture and imaging element for use within a solid state image sensor. Solid state image sensors predicated upon CMOS semiconductor devices are generally desirable insofar as such CMOS based solid state image sensors may consume less power in comparison with other types of solid state image sensors. Moreover, CMOS based solid state image sensors allow for fabrication of CMOS based electrical support circuit components simultaneously with CMOS based solid state image sensor components.
While solid state image sensors in general, and CMOS image sensors more particularly, are desirable within the optoelectronic component fabrication art, solid state image sensors in general; and CMOS image sensors more particularly, are not entirely without problems. In particular, performance enhancements, such as dynamic range performance enhancements, are often desirable within solid state sensors in general and solid state image sensors more particularly, in order to provide for accurate and high contrast images.
Various solid state sensor structures and designs, and methods for fabrication thereof, are known in the optoelectronic art.
For example, Bock, in U.S. Pub. No. 2004/0436784, teaches a CMOS pixel sensor cell that includes, among other features, a wide dynamic range. This particular CMOS pixel sensor cell provides the wide dynamic range through use of a three phase operating methodology.
In addition, Boemler, in U.S. Pub. No. 2005/0224843, U.S. Pat. No. 7,091,531 and U.S. Pub. No. 2006/0243887, teaches another CMOS pixel sensor cell with a wide dynamic range. This particular CMOS pixel sensor cell provides the wide dynamic range through use of a floating diffusion that has a variable capacitance.
Solid state sensors, including charge coupled device (CCD) image sensors and further including in particular complementary metal oxide semiconductor (CMOS) image sensors, are likely to be of continued interest and continued importance as solid state sensor technology advances. Thus, desirable are solid state sensors, design structures for fabrication thereof and methods for operation thereof, as well as related component sub-structures, that provide for improved performance, including enhanced dynamic range capabilities.